Storage battery with heater

ABSTRACT

A storage battery comprising electrode plate groups including anode plates and cathode plates, a battery casing for accommodating said electrode plate groups and electrolyte, a closure covering said battery casing, and face heaters so treated as to be of electrolyte-resistance and provided in said battery casing, wherein said electrolyte is effectively heated to prevent the electromotive force from being decreased due to a decrease in temperature of said electrolyte, thereby producing a constant electromotive force.

United States Patent 1 Toydoka et al. v

STORAGE BATTERY WITH HEATER Inventors: Tadao Toydoka, 16-6,Oshimachol-chome; Takeo Nishida, c/o Shizu- Filed:

hoso of Honancho, both 72, Nishi-S-chome,

of Toyonaka;

Hiroshi lchihara, 1758, Kameino, Fujisawa, all of Japan Jan. 8, 1971Appl. No.: 105,004

Related U.S. Application Data Division of Ser. No. 708,676, Feb. 27,1968, Pat. No. 3,623,916.

, Foreign Application Priority Data Mar. Mar. M ar. Mar. M ar. Mar. Mar,M ar. Mar. M ar. Mar.

Mar. 27, 1967 Mar. 27, 1967 Japan ..42/18199 Japan ..42/18214 Japan..42/18215 Japan ..42/18216 Japan .Q ..42/18217 Japan 42/l8218 Japan..42/18220 Japan ..42/18221 Japan ..42/18222 Japan ..42/18223 Japan..42/20258 Japan ..42/19752 Japan ..42/19753 1 Mar. 27, 1973 [52] U.S.Cl ..136/161 [51] Int. Cl. ..H0lm 45/02 [58] Field of Search ..136/161[56] References Cited- UNITED STATES PATENTS 2,516,048 7/1950 Endress.,..136/161 FOREIGN PATENTS OR APPLICATIONS 894,555 4/1962 Great Britain..136/161 Primary Examiner-Donald L. Walton Attorney-Stevens, Davis,Miller & Mosher [57] ABSTRACT A storage battery comprising electrodeplate groups including anode plates and cathode plates, a battery casingfor accommodating said electrode plate groups and electrolyte, a closurecovering said battery casing, and face heaters so treated as to be ofelectrolyte-resistance and provided in said battery casing, wherein saidelectrolyte is effectively heated to prevent the electromotive forcefrom being decreased due to a decrease in temperature of saidelectrolyte, thereby producing a constant electromotive force.

5 Claims, 22 Drawing Figures SHEET 1 OF 8 PATENTEDHARZYIHYS INVENTORSTADAO TOYOOKA TAK EO NISHIDA HIROSHI ICHIHARA BY 5 ATTORNEYS PmaminmznmSHEET 0F 8 i I I I I I I I I I I I I I I I I I i S PATENTEDHARZYISTS 387 SHEET 5 OF 8 III' SHEET 8 BF 8 /7 :umum

PATENTEDHARZTIBTS STORAGE BATTERY WITH HEATER CROSS-REFERENCES TORELATED APPLICATION This application is a division of U.S. Pat.application Ser. No. 708,676 filed on Feb. 27, 1968, now U.S. Pat. No.3,623,916.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a storage battery, and more particularly it pertains to suchbattery including face heaters provided in a battery casing toeffectively heat electrolyte for the purpose of preventing a decrease inthe electromotive force, thereby producing a constant electromotiveforce.

2. Description of the Prior Art As well known, the electromotive forceof a storage battery is produced by virtue of a kind of chemicalreaction. Thus, such electromotive force may be considerably decreasedat low temperatures as in winter since the temperature of the batteryitself, especially the temperature of the electrolyte in influenced bythe ambient temperature. The reaction velocity of electrolyte dependsupon temperature, and it is lowered at low temperatures so that theelectromotive force is decreased. If, for example, the electromotiveforce is 100 at 20C., it will be decreased down to 50 at l C.

Such an effect of the low ambient temperature on electrolyte can beeliminated by heating the battery in winter so that the electromotiveforce may be prevented from being decreased at low temperatures, thusproducing a constant electromotive force all the time.

In view of such point, attempts have conventionally been made to heat astorage battery by the use of heating means.

In accordance with conventional batteries, however, such heating meansis embedded in the battery casing or it is provided on the outer surfaceof the casing.

Obviously, the former arrangement is disadvantageous in that muchtrouble is experienced in forming the battery casing or it is requiredto replace the battery casing itself in case the heating means is partlydamaged. Furthermore, the heat produced by the heating means isconsiderably wasted to heat the battery casing itself, which leads to alower thermal efficiency. The latter arrangement has such drawbacks thatthe heat loss is so great that the thermal efficiency is low because thestorage battery is internally heated through the battery casing and theheating means is exposed to the outside.

SUMMARY OF THE INVENTION An object of this invention is to provide astorage battery in which face heaters so treated as to be ofelectrolyte-resistance are immersed directly in the electrolytecontained in the battery casing to effectively heat the electrolyte overa wide range thereby preventing a decrease in the electromotive force.

Another object of this invention is to provide a storage batterycomprising electrode plate groups including anode plates and cathodeplates, a battery casing accommodating therein said electrode plategroups and electrolyte, a closure covering said battery casing,

and face heaters so treated as to be of electrolyte-resistance andprovided in said battery casing.

Other objects, features and advantages of the present invention will bereadily apparent from the following detailed description of certainpreferred embodiments taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective view of astorage battery according to this invention.

FIG. 2 is a perspective view showing the lead wire connecting portion ofthe storage battery shown in FIG.

FIG. 3 is an enlarged sectional view showing the main portion of thestorage battery shown in FIG. 1.

FIG. 4 is a front view showing a group of electrode plates used in thestorage battery shown in FIG. 1.

FIG. 5 is a side view thereof.

FIG. 6 is a front view showing an example of the face heater provided inthe storage battery shown in FIG. 1.

FIG. 7 is a perspective view showing an example of the active materialsupporting means provided in the storage battery shown in FIG. 1.

FIG. 8 is a partially broken front view showing a second example of theface heater provided in the storage battery shown in FIG. 1.

FIG. 9 is a longitudinal sectional view of the face heater shown in FIG.8.

FIG. 10 is a front view showing a third example of the face heater foruse with the storage battery embodying this invention.

FIG. 11 is a sectional view taken along line AA of FIG. 10.

FIG. 12 is a perspective view showing a fourth example of the faceheater for use with the storage battery embodying this invention.

FIG. 13 is an enlarged perspective view showing a heating coil providedin the face heater.

FIG. 14 is a perspective view showing the main portion of a batterycasing provided in the storage battery embodying this invention.

FIG. 15 is a sectional view showing the battery casing, taken along lineBB of FIG. 14 together with a closure provided on the casing.

FIG. 16 is a sectional view showing an example of the connection betweenlead wires and the face heater.

FIG. 17 is a sectional view showing a second example of the connectionbetween the lead wires and the face heater.

FIG. 18 is a sectional view showing a third example of the connectionbetween the lead wires and the face heater.

FIG. 19 is a sectional view showing the storage battery of thisinvention provided with a temperature controller.

FIG. 20 is a sectional view showing the main portion of the storagebattery provided with a different temperature controller.

FIG. 21 is a top plan view of FIG. 20.

FIG. 22 is a diagram showing the circuit arrangement of each of thestorage batteries shown in FIGS. 20 and 21.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. 1 to 6,description will be made of the major construction of the presentinvention.

As shown in the drawings, a battery casing 1 is divided into a pluralityof unit battery casings 3 by means of partition walls 2. In each of theunit battery casings 3 are inserted a group of electrode plates 4including anode plates 5, cathode plates 6, separators 7 and activematerial supporting members 8. The active material supporting members 8are disposed in contact with the reaction surfaces of the anode plates 5to prevent removal of the active material thereby retaining the latterin place. Such supporting members are normally formed of a glass mat.Separators 7 are formed by an ion-permeable layer of which the surfacesare of electric insulation, and they cover from opposite sides the anodeplates 5 having the opposite surfaces disposed in contact with thesupport members 8. That is, the separators 7 and the support members 8are interposed between the anode plates 5 and the cathode plates 6 insuch a manner that the support members 8 are disposed in contact withthe anode plates 5. The reference numeral 9 represents shelves eachplaced in contact with the electrode plates of the same polarity of theelectrode group 4, 10 electrode poles for the electrode group 4, llelectrolyte which is contained in the unit battery casings 3 togetherwith the electrode group 4, and 12 face heaters inserted between theopposite outermost electrode plates of each electrode group 4 and thepartition walls or the inner walls of the battery casing. The referencenumeral 13 denotes a closure covering the battery casing l and providedon the inner surface opposing the battery casing l and the front ends ofthe partition walls 2 with projections 14 which are formed with recessedgrooves 15 engaged by the front ends of the partition walls 2. Thereference numeral 16 indicates an insulating and electrolyte-resistingadhesive agent filled in the recessed grooves 15 to integrally andliquid-tightly fix the battery casing l and the closure 13 to eachother, and the reference numeral 17 represents inlets for pouring theelectrolyte into the unit battery casings 3.

The aforementioned face heater 12 is formed by weaving a heating wire 19together with heat-resisting warps and wefts to form a heating cloth asshown in FIG. 6 and thereafter embedding the heating cloth inelectrolyte-resisting synthetic resin 18 such as polyethylene in asandwich-like manner. The power source for the face heaters 12 may beeither the storage battery itself or a separate one.

For the heating wire of the face heater, use may be made of a conductiveresistance metal wire such as stainless wire, a carbon fiber, a yarnhaving graphite, carbon or the like applied on the surface thereof, orthe like.

Instead of the heating cloth constituting the face heater 12, use mayalso be made of a face resistor formed by a mixture of conductive powdersuch as metal powder, graphite powder or the like and a resin.

In the storage battery described above, the electrolyte l1 filled in therespective unit battery casings is directly and uniformly heated over awide range by flowing an electric current through the face heater 12,

thereby making it possible to effectively prevent the electromotiveforce of the storage battery from being decreased, for example, inwinter.

Several examples of the face heater 12 will be described hereinbelow.Various types of construction of the face heater 12 may be possible, andtherefore it is to be understood that the present invention is notlimited to the examples described below.

In the example of FIG. 6, use was made of filaments of 240d made ofsynthetic fiber for the warps, staple yarns of 20 SH made of syntheticfiber for the wefts, and a stranded wire formed by twisting yarnstwisted at a rate of 470 turns/m with a heater strand for the heatingwire which was woven together with the warps and the wefts.

In order to use the heating cloth thus produced, such heating cloth isimpregnated with a synthetic resin so that it is embedded in the latter,it is held between two sheets of cushion base cloth such as glass mat,glass cloth or the like to cover the surfaces thereof with the latter,or it is held between two synthetic resin plates to insulate thesurfaces thereof.

In the case of the face heater 12 shown in FIG. 6, the heating cloth washeld between two sheets of polyvinyl chloride and made integral with thesheets by attaching the edge portions of the sheets to each other.

Then the heating cloth was embedded in polyester phtalate maleate resinas follows.

A preparation was made for two tempered glass plates of a predeterminedsize, and a mold releasing agent such as polyvinyl alcohol was thinlyapplied on the molded surfaces of the plates. Then, polyester phtalatemaleate resin was applied on the glass plates having the mold releasingagent thereon as described above, and thereafter styrene monomer wassprayed onto the resin surfaces by means of a sprayer so as to removeair bubbles present in the resin. Subsequently, styrene was applied onthe heating cloth after the resin solidified to such an extent that itjellified, and then the heating cloth was placed on the jellified resin.A small quantity of polyester phtalate maleate resin was uniformlyapplied on the heating cloth, and then styrene was applied thereon thusremoving air bubbles.

Another glass plate having polyester phtalate maleate resin appliedthereon was gradually placed on the heating cloth in such a manner thatthe jellified resin lies on the heating cloth and no air bubbles remain.Under a pressure of l Kg/cm the unit was left until the inside resinjellified, and thereafter it was heated to a temperature of 60 C. andhardened in 10 20 minutes.

The unit was naturally cooled down to about 40C. after having beenhardened, and then the tempered glass plates on the opposite sides ofthe unit were removed. Thus, a complete face heater was produced.

Description will now be made of the face heater 12 shown in FIGS. 8 and9.

In this face heater, use was made of electrolyte-resisting fiber such,for example, as glass fiber for warps 20 and an electrolyte-resistingheating wire 19 and glass fiber for wefts 21 woven together with thewarps 20. More specifically, the warps 20 and wefts 21 were formed bybundling 225 pieces of glass fiber 7 microns in diameter and twistingthem 1.7 times per 2.5 mm on the average. The warps 20 had the oppositeend portions cut off, whereas the heating wire 19 forming part of thewefts 21 was bent, without being cut off, at the opposite ends so as tobe woven in a zigzag manner. Singular power supply terminals 23, 23 areembedded in the center of an electrolyte-resisting insulator 24. In thiscase, thirty pieces of the warps 20 and wefts 21 may be used per 2.5 mm,and adjacent portions of the heating wire 19 may be spaced apredetermined distance (insulating distance).

Next, description will be made of an example of the case where the faceheater 12 is made to be transparent. That the face heater 12 istransparent is not only advantageous in respect of the maintenance ofthe storage battery because it is possible to look into the inside ofthe battery casing when made of a transparent material but also producessuch an effect as to promote the reaction of the electrolyte because thetemperature of the electrolyte is raised by light rays coming in throughthe face heater.

In this example, the warps and wefts were prepared by bundling 225pieces of non-alkaline glass fiber and twisting them together 1.7 timesper 2.5 mm on the average. Thirty pieces of such warps and wefts werewoven together with fine metal wires arranged at uniform intervals toform a cloth, which in turn was subjected to heat treatment at 340C. for30 hours, and the bundling agent adhering to the glass fiber was burntto be removed. Thereafter, the cloth was cooled and applied with styrenemonomer. Then it was embedded in transparent maleic polyester phtalateresin. The embedding method was such that two tempered glass plates of apredetermined size were first prepared and then a mold releasing agentsuch as polyvinyl alcohol was very thinly applied on the molded surfacesof the glass plates. The application of the mold releasing agent waseffected in such a manner as to polish the glass plates with the moldreleasing agent, thereby removing cloudiness, stains, etc. Apredetermined quantity of compound maleic polyester phtalate resin(trade name, non-saturated polyester No. 8009 or 8010 produced byDainippon Ink Kagaku Kogyo Kabushiki Kaisha) was uniformly applied onthe glass plates having the mold releasing agent applied thereon, andthen styrene monomer was lightly sprayed on the resin surface by meansof a sprayer to remove air bubbles present in the resin which startedsolidification in odd minutes. When the resin jellified, styrene wasapplied on the glass fiber cloth having the fine metal wires woventherein, and it was placed on the jellified resin. Thereafter, a smallquantity of maleic polyester phtalate resin was uniformly applied on thecloth and also styrene was applied thereon to remove air bubbles.Another glass plate having maleic polyester phtalate resin appliedthereon was gradually placed on the cloth in such a manner that thejellified resin lies on the cloth. Then the unit was maintained under apressure of l Kg/cm until the inside resin jellified. Thereafter, theunit was heatedat 60 80C. so that it was completely hardened as a wholein 10 minutes. After having been hardened, the unit was subjected tonatural cooling down to about 40C., and the tempered glass platesprovided on the opposite sides thereof were removed. Thus, the completeface heater was assembled. The transparentmember having theaforementioned fine metal wire embedded therein becomes transparent whenthe glass fiber cloth with a luster characteristic of glass fiber isembedded in the polyester resin that only the fine metal wire woven inthe glass fiber cloth as part of the wefts can be seen. Thus, thetransparency can be increased by 83 percent. In this case, themeasurement of the transparency was performed at a wavelength of 600millimicrons with the aid of a Beckman spectrophotometer.

Although in the foregoing the face heater 12 has been described withrespect to several specific embodimen'ts, it is to be understood thatthe face heater is by no means restricted to such specific embodiments.The most important point is that the heater is covered'with a resin.

If a heating wire is woven together with warps in the center of a clothformed by weaving the warps and wefts and wefts together in case use ismade of only heating wire in each heating cloth as described above, theheating wire supplied from a shuttle is unwound from a bobbin or thelike to become helical. Therefore, if the helical heating wire is drawnas it is, a kink (twist) will be caused in it. Weaving the heating wirein such a state tends cut off the heating wire during the weavingoperation or cause the heating wire to be projected out of the resinsurface in case the heating cloth is embedded in the resin, even thoughthe weaving operation is completed with a kink imparted to the finishedcloth. This results in a defective insulating coding so that the heatingwire tends to be corroded by the electrolyte.

In order to avoid such drawbacks, therefore, the face heating 12 ispreferably formed by the use of a heating wire 19 consisting of a heaterwire 30 and a kink preventing yarn 31 which are pre-twisted in theopposite direction to the aforementioned helical direction. By doing so,the heating wire supplied from the shuttle is linearly drawn out withoutbecoming helical, so that-no kink will be caused. That is, the heaterwire 30 is pre-twisted through the kink preventing yarn in the oppositedirection to the helical direction. From the stand point of handlingconvenience, great advantage can be obtained by making the weavingdensity in an edge portion of the cloth more than that in the remainingportion in the formation of the face heater 12. In the case of the faceheater as shown in FIG. 12, the handling of it can be facilitated bymaking the density of the warps in the positions where the heater wire19 is folded back, because by doing so it is possible to prevent thecloth from wrinkling even at the foldedback portions of the heating wire19. This also makes it possible to embed the cloth in the resin at adesired position without deformation.

Although the heating wire may be distributed uniformly at the top andbottom, it is preferable that the density of the heating wire 19 isincreased toward the bottom predominantly in order to heat the deeperportion of the electrolyte, as shown in FIG. 12. By doing so, theconvection effect of the electrolyte is promoted so that the heatretaining of the electrolyte can be effectively achieved andsimultaneously the reaction of the electrolyte can be uniformlyeffected, thus increasing the electromotive force.

By providing at such a position as shown in FIG. 3 a face heater 12which is constructed not in the form ofa flat plate but in such a mannerthat it is formed with a plurality of longitudinal projecting strips 35as shown in FIGS. and 11, it is also possible to cause the electrolyteto freely pass through between the face heater and the electrode group4. Thus, the electrolyte can be effectively heated so that theperformance can be improved.

Each face heater 12 is provided in each unit battery casing 3 togetherwith the electrode group 4 in such a manner that it serves also as aspacer.

However, it is to be understood that the position of the face heater 12can be freely selected, and it is by no means limited to the above. Forexample, it has been found that the temperature is more greatlydecreased in the battery casing side portions of the storage batterythan in' the other portions, and that such decrease in temperature hasgreat effect on the decrease in the electromotive force of the battery.By providing the face heater 12 in the side portion of the batterycasing 1, therefore, it is possible to retain heat predominantly in suchside portion and effectively prevent decrease in the electromotive forceof the storage battery.

Also, the face heater 12 can be incorporated in each partition wall 2since it can also be used as such wall in the battery casing 1. Withsuch arrangement, the capacity of the battery casing will never bereduced irrespective of the present of the face heater 12, so that itcan be effectively utilized to advantage.

Furthermore, the face heater 12 can also be used as either the separator7 or the active material supporting member 8 described in connectionwith FIG. 5. In this case, the electrode plates 5 and 6 and theelectrolyte 11 are heated directly by the face heater so that heat canbe effectively retained therein, thus preventing decrease in theelectromotive force of the storage battery. In the case where the faceheater 12 is used as the active material supporting member 8, glass mats36, 36 are placed in contact with the opposite surfaces of the faceheater 12, as shown in FIG. 7. If the face heater 12 itself has asufficient cushioning property or if, for example, the heating cloth isheld between cushion base plates, it is not necessary to superpose theglass mats 36, 36 on the face heater.

Description will now be made of the method for treating and sealing thelead wires of the face heater 12.

The face heater 12 has its ear portions 37 projected upwardly, and it islocated above the partition walls 2. An example of such arrangement isshown in FIGS. 14 and 15. Terminals 38 taken out from the respective earportions 37 are connected in parallel with each other. Said ear portions37 are disposed in engagement with recessed grooves 15 formed in thebattery closure, and thereafter an electrolyte-resisting insulatingadhesive agent such as epoxy resin is filled in the recessed grooves 15,thereby fixed the closure integrally with the battery casing l. Theterminals 38 and the lead wires 39 are also protected. It will bereadily apparent that the lug portions 37 of the face heater 12 may befixed to the battery casing closure 13 instead of fixing the closure 13to the battery casing l.

Other examples of the method of sealing the lead wires are shown inFIGS. l7, l8 and 19.

In FIG. 16, electrolyte-resisting resin tubes 40 are thermally fixed tothe face heater 12 at the opposite sides thereof and have their upperend portions projected out of the closure 13 for the battery casing l inthe neighborhood of the side edge portions. In the resin tubes 40 areinserted terminals 38 with which are connected lead wires 39, and theconnection portions are embedded in an electrolyte-resisting andinsulating compound 41 formed, for example, by pitch so as to beinsulated thereby.

In FIG. 17, the battery casing closure 13 is formed with a recessedgroove 42 in addition to those 15 for fixing the closure 13 to thebattery casing 1, and the face heater 12 has its lug portions 37inserted in the recessed groove 42, which in turn is filled with anelectrolyte-resisting and insulating adhesive agent 43 after the leadwires 39 have been connected with the terminals 38.

In FIG. 18, the lug portions 37 of the face heater 12 are caused topenetrate through the battery casing closure 13 so that the upper endsof the lug portions 37 are exposed in recessed grooves 44 formed in theupper surface of the battery casing closure 13. The recessed grooves 44are filled with an electrolyte-resisting and insulating adhesive agent45 after the lead wires 39 are connected with the terminals 38.

As will be seen from FIGS. 14 through 18, the face heater 12 is formedwith one lug portion in some cases and with two lug portions in othercases, but it is to be understood that the essence of the present natureof the present invention is not changed by such difference.

The lead wires 39 connected with the face heater 12 are taken outthrough the closure 13 and connected with positive and negativeterminals 46 and 47 provided on the battery casing closure 13,respectively.

Besides the above, such an arrangement shown in FIGS. 1 and 2 is alsopossible in which the lead wires 39 are connected with the terminals 38of the face heater 12 in a recessed groove 48 formed in the uppersurface of the battery casing closure 13, then the recessed groove 48 isfilled or applied with an adhesive agent, and a cover 49 is fitted onthe closure 13 through the adhesive agent to fix the connection of thelead wires thereby preventing the lead wires from being cut off and theconnection from becoming defective as well as protecting the lead wiresfrom external shock.

As described above, the face heater according to the present inventionis characterized by being very thin so that the insertion of the faceheater into each unit battery casing does not reduce the capacity of aconventional storage battery, and the storage battery embodying thepresent invention is characterized by being able to always produce aconstant electromotive force even at low temperatures.

Description will now be made of the temperature controller for use withthe storage battery according to the present invention.

Referring to FIGS. 14 and 15, there is provided on the inner wall of thebattery casing a sealed container 50 made of an electrolyte-resistingmaterial accommodating therein a bimetal switch connected in series withthe lead wires 39. By filling an oil such for example as silicone oil inthe container 50 together with the bimetal switch, it is possible toprevent the occurrence of spark in the making or breaking of thecontacts thereby increasing the useful life of the switch as well as todecrease vibrations of the bimetal contacts in the case of a mobilebattery. Although it is most preferable to immerse the container 50 inthe electrolyte, it is also possible to provide such container on thelower surface of the battery casing closure 13 or embed it in a sealingcompound.

The bimetal switch accommodated in the afore-mentioned container 50 isso designed that its contacts are opened if the electrolyte isunnecessarily overheated thereby preventing the power from beingwastefully consumed and the electrolyte from being evaporated.

Other examples will be described with reference to FIGS. 20, 21 and 22.The reference numeral 51 represents a thermostat provided in a recessedgroove 52 formed in the battery casing closure 13, and it comprises acase 55 including a conductive cover 53 and a bottom plate 54, a fixedcontact 56, a movable contact 57 energized so as to be normally disposedin contact with the fixed contact 56, and a bimetal 58 adapted to causethe movable contact 57 to be disposed out of the fixed contact 56 whenit is bent. The fixed contact 56 is connected with one of the terminalsof the face heater l2, and the movable contact 57 is connected with theother terminal of the face heater 12 through switch 59 and power source60.

Thus, by supplying power to the face heater with the switch closed, theelectrolyte is heated thereby, so that the electromotive force of thestorage battery can be prevented from being decreased at lowtemperatures. The temperature within the battery is transmitted also tothe thermostat 51 through the battery casing closure 13, and if suchtemperature is excessively raised, the bimetal 58 is bent to bring themovable contact away from the fixed contact, thereby interrupting thepower supply to the face heater 12.

Since the battery casing closure 13 is usually made of a material of alow heat conductivity such as bakelite, ebonite or the like, it isrequired that the spacing between the fixed contact 56 and the movablecontact 57 and the expansion coefficient of the metal forming thebimetal 58 be selected accordingly. FIG. 22 shows an example of theelectric circuit in which the respective face heaters 12 are connectedin parallel with each other and the thermostat 51, the switch 59 and thepower source 60 are connected in series with the parallelly connectedface heaters 12.

The switch 59 described above is not essentially required, while it maybe provided on the top of the battery casing closure 13 as shown in FIG.2.

Although in the foregoing description mention has been made of the casewhere the bimetal is used as the temperature controller, it ispossibleto produce a similar effect by the use of a posistor instead of thebimetal.

In FIG. 19, the reference numeral 61 represents a posistor accommodatedin a container 62 which is liquidtightly provided on the battery casingclosure 13, and located in the electrolyte. The posistor 61 is connectedwith power source 63 and terminals 38 of the face heater 12.

Since the posistor 61 described above has such a nature that itrepresents a low electric resistance when the ambient temperature is lowwhile it represents a high electric resistance when the ambienttemperature is high, the power supply to the face heater 12 can becontrolled in accordance with variations in the ambient temperature asin the case where a bimetal is used, so

that the electrolyte can be maintained at a predetermined temperature,thereby preventing the electromotive force from being decreased.

As Wlll be appreciated from the foregoing, with the storage batteryaccording to the present invention, it is possible to prevent theelectromotive force from being decreased even at low temperatures as inwinter, so that a constant electromotive force can always be produced.

We claim:

1. A storage battery comprising electrode plate groups including anodeplates and cathode plates, electrolyte, a battery casing foraccommodating therein said electrode plate groups and said electrolyte,a battery casing closure covering said battery casing and face heatersfor heating said electrolyte; wherein said face heaters comprise aheating wire formed from a resistance wire and kink preventing yarntwisted together, and a heat-resistant cloth of said heating wire woventogether with heat-resistant wefts and warps, said face heaters beingelectrolyte-resistant and interposed between said electrode plate groupsand partition walls dividing the inside of said battery casing in closecontact therewith; lead wires connected with said face heaters beingdisposed in a recessed groove of said battery casing closure providedconfronting with the open end of said battery casing and said partitionwalls, and means insulating said lead wires in said recessed groove,said lead wires being connected with a power source.

2. A storage battery as defined in claim 1, wherein said face heatershave a high weave density portion formed in one edge portion of saidheat-resistant cloth with said heating wire woven thereinto.

3. A storage battery as defined in claim 1, wherein said heating wire isdistributed more densely toward the bottom than the top of said faceheaters.

4. A storage battery as defined in claim 1, wherein said lead wiresconnected with said face heaters are embedded in an insulating andelectrolyte-resistant adhesive means, said adhesive means adhering saidbattery casing closure to said battery casing.

5. A storage battery as defined in claim 1, wherein said lead wiresconnected with said face heaters are embedded in a sealing compound forsealing said battery casing and said battery casing closure.

2. A storage battery as defined in claim 1, wherein said face heatershave a high weave density portion formed in one edge portion of saidheat-resistant cloth with said heating wire woven thereinto.
 3. Astorage battery as defined in claim 1, wherein said heating wire isdistributed more densely toward the bottom than the top of said faceheaters.
 4. A storage battery as defined in claim 1, wherein said leadwires connected with said face heaters are embedded in an insulating andelectrolyte-resistant adhesive means, said adhesive means adhering saidbattery casing closure to said battery casing.
 5. A storage battery asdefined in claim 1, wherein said lead wires connected with said faceheaters are embedded in a sealing compound for sealing said batterycasing and said battery casing closure.